fix alt-screen scrollback handling

1 files changed, 179 insertions, 0 deletions

diff --git a/vendor/vt100/src/cell.rs b/vendor/vt100/src/cell.rs
new file mode 100644
index 00000000..c000cf30
--- /dev/null
+++ b/vendor/vt100/src/cell.rs
@@ -0,0 +1,179 @@
+use unicode_width::UnicodeWidthChar as _;
+
+// chosen to make the size of the cell struct 32 bytes
+const CONTENT_BYTES: usize = 22;
+
+const IS_WIDE: u8 = 0b1000_0000;
+const IS_WIDE_CONTINUATION: u8 = 0b0100_0000;
+const LEN_BITS: u8 = 0b0001_1111;
+
+/// Represents a single terminal cell.
+#[derive(Clone, Debug, Eq)]
+pub struct Cell {
+    contents: [u8; CONTENT_BYTES],
+    len: u8,
+    attrs: crate::attrs::Attrs,
+}
+const _: () = assert!(std::mem::size_of::<Cell>() == 32);
+
+impl PartialEq<Self> for Cell {
+    fn eq(&self, other: &Self) -> bool {
+        if self.len != other.len {
+            return false;
+        }
+        if self.attrs != other.attrs {
+            return false;
+        }
+        let len = self.len();
+        self.contents[..len] == other.contents[..len]
+    }
+}
+
+impl Cell {
+    pub(crate) fn new() -> Self {
+        Self {
+            contents: Default::default(),
+            len: 0,
+            attrs: crate::attrs::Attrs::default(),
+        }
+    }
+
+    fn len(&self) -> usize {
+        usize::from(self.len & LEN_BITS)
+    }
+
+    pub(crate) fn set(&mut self, c: char, a: crate::attrs::Attrs) {
+        self.len = 0;
+        self.append_char(0, c);
+        // strings in this context should always be an arbitrary character
+        // followed by zero or more zero-width characters, so we should only
+        // have to look at the first character
+        self.set_wide(c.width().unwrap_or(1) > 1);
+        self.attrs = a;
+    }
+
+    pub(crate) fn append(&mut self, c: char) {
+        let len = self.len();
+        if len >= CONTENT_BYTES - 4 {
+            return;
+        }
+        if len == 0 {
+            self.contents[0] = b' ';
+            self.len += 1;
+        }
+
+        // we already checked that we have space for another codepoint
+        self.append_char(self.len(), c);
+    }
+
+    // Writes bytes representing c at start
+    // Requires caller to verify start <= CODEPOINTS_IN_CELL * 4
+    fn append_char(&mut self, start: usize, c: char) {
+        c.encode_utf8(&mut self.contents[start..]);
+        self.len += u8::try_from(c.len_utf8()).unwrap();
+    }
+
+    pub(crate) fn clear(&mut self, attrs: crate::attrs::Attrs) {
+        self.len = 0;
+        self.attrs = attrs;
+    }
+
+    /// Returns the text contents of the cell.
+    ///
+    /// Can include multiple unicode characters if combining characters are
+    /// used, but will contain at most one character with a non-zero character
+    /// width.
+    // Since contents has been constructed by appending chars encoded as UTF-8 it will be valid UTF-8
+    #[allow(clippy::missing_panics_doc)]
+    #[must_use]
+    pub fn contents(&self) -> &str {
+        std::str::from_utf8(&self.contents[..self.len()]).unwrap()
+    }
+
+    /// Returns whether the cell contains any text data.
+    #[must_use]
+    pub fn has_contents(&self) -> bool {
+        self.len() > 0
+    }
+
+    /// Returns whether the text data in the cell represents a wide character.
+    #[must_use]
+    pub fn is_wide(&self) -> bool {
+        self.len & IS_WIDE != 0
+    }
+
+    /// Returns whether the cell contains the second half of a wide character
+    /// (in other words, whether the previous cell in the row contains a wide
+    /// character)
+    #[must_use]
+    pub fn is_wide_continuation(&self) -> bool {
+        self.len & IS_WIDE_CONTINUATION != 0
+    }
+
+    fn set_wide(&mut self, wide: bool) {
+        if wide {
+            self.len |= IS_WIDE;
+        } else {
+            self.len &= !IS_WIDE;
+        }
+    }
+
+    pub(crate) fn set_wide_continuation(&mut self, wide: bool) {
+        if wide {
+            self.len |= IS_WIDE_CONTINUATION;
+        } else {
+            self.len &= !IS_WIDE_CONTINUATION;
+        }
+    }
+
+    pub(crate) fn attrs(&self) -> &crate::attrs::Attrs {
+        &self.attrs
+    }
+
+    /// Returns the foreground color of the cell.
+    #[must_use]
+    pub fn fgcolor(&self) -> crate::Color {
+        self.attrs.fgcolor
+    }
+
+    /// Returns the background color of the cell.
+    #[must_use]
+    pub fn bgcolor(&self) -> crate::Color {
+        self.attrs.bgcolor
+    }
+
+    /// Returns whether the cell should be rendered with the bold text
+    /// attribute.
+    #[must_use]
+    pub fn bold(&self) -> bool {
+        self.attrs.bold()
+    }
+
+    /// Returns whether the cell should be rendered with the dim text
+    /// attribute.
+    #[must_use]
+    pub fn dim(&self) -> bool {
+        self.attrs.dim()
+    }
+
+    /// Returns whether the cell should be rendered with the italic text
+    /// attribute.
+    #[must_use]
+    pub fn italic(&self) -> bool {
+        self.attrs.italic()
+    }
+
+    /// Returns whether the cell should be rendered with the underlined text
+    /// attribute.
+    #[must_use]
+    pub fn underline(&self) -> bool {
+        self.attrs.underline()
+    }
+
+    /// Returns whether the cell should be rendered with the inverse text
+    /// attribute.
+    #[must_use]
+    pub fn inverse(&self) -> bool {
+        self.attrs.inverse()
+    }
+}